Essential Evidence-based Medicine, Second Edition (Essential ...

384
Appendix 2 Overview of critical appraisal
Adapted from G. Guyatt & D. Rennie (eds.) Users’ Guides to the Medical Literature: a Manual
for Evidence-Based Clinical Practice. Chicago: AMA, 2002. Used with permission.
(1) Randomized clinical trials (commonly studies of therapy or prevention)
(a) Are the results valid?
(i) Were the patients randomly assigned to treatment and was allocation effectively
concealed?
(ii) Were the baseline characteristics of all groups similar at the start of the study?
(iii) Were the patients who entered the study fully accounted for at its conclusion?
(iv) Were participating patients, family members, treating clinicians, and other
people (observers or managers) involved in the study “blind” to the treatment
received?
(v) Were all measurements made in an objective and reproducible manner?
(vi) With the exception of the experimental intervention, were all patients treated
equally?
(vii) Were the patients analyzed in the groups to which they were randomized?
(viii) Was follow-up complete?
(b) What are the results?
(i) What is the treatment effect? (Absolute Rate Reduction, Relative Rate Reduction,
Number Needed to Treat)
(ii) What is the variability of this effect? (Confidence Intervals)
(c) Will the results help me in my patient care?
(i) Were all clinically important outcomes considered in the study?
(ii) Will the benefits of the experimental treatment counterbalance any harms
and additional costs?
(iii) Can the results of this study be applied to most of my patients with this or
similar problems?
(2) Cohort studies (commonly studies of risk or harm or etiology)
(a) Are the results valid?
(i) With the exception of the risk factor under study, were all groups similar to each
other at the start of the study?
(ii) Were all measurements (outcome and exposure) made in an objective and
reproducible manner and carried out in the same ways in all groups?